Mature hardened cement paste

As the chemical reactions in the paste will continue even after setting, the hardness and strength of the paste—which are low immediately after setting— will increase, and a hardened cement paste will be formed. Ultimately the hardening reaction in the paste comes to an end, owing to the complete consumption of the original binder or insufficient amounts of mixing liquid, and a mature hardened cement paste results. 

Hardened Portland cement contains a distribution of pore and capillary sizes, depending on the initial water-cement ratio and the maturity of the paste. A typical distribution of pore radii in the hardened cement paste of concrete was shown in Fig. 1.40 which indicated that the majority of pores he in the region of 0.05 and 1.0 pm diameter and it is through these pores that water passes by applied pressure or capillary rise, as shown in Fig. 4.5 (a). 

Hardened Portland cement contains a distribution of pore and capillary sizes, depending on the initial water-cement ratio and the maturity of the paste. 

The texture of cement pastes in high-performance concretes is characterized by high density and very low porosity. Owing to the pozzolanic reaction between the added microsilica and calcium hydroxide, the amount of ciystalline portlandite in the hardened paste is reduced, and the formed C-S-H phase has a lower C/S ratio (Cheong et al, 1997). The mature cement paste contains a significant fraction of non-hydrated cement. 

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